Human Cytomegalovirus Inhibits Granulopoiesis Via Direct Infection and Inducing Apoptosis.

Human cytomegalovirus (HCMV) infection can cause delayed leukocyte recovery after bone marrow transplantation and often associated with suppression of granulocyte/macrophage progenitor. Leukocyte lineage may be one of the major sites of HCMV infection. However, whether HCMV can interfere with CFU-GM formation and induce apoptosis in granulocyte/macrophage progenitor have not been well investigated. Human bone marrow mononuclear cells (Ficoll), promyelocyte cell line HL-60 and HCMV AD169 strain were co-cultured. Each bone marrow specimen was HCMV DNA and HCMV IgM negative by PCR and ELISA test. Our results showed that HCMV significantly inhibited the formation of CFU-GM as shown in two different concentrations of viral infection groups: 139.26 ± 5.42 (2×105pfu/ml), and 124.19 ± 8.82 (2×106pfu/ml) (colonies/2×105cells/ml, n=26). These were significant differences compared with the blank control group (P<0.01, P<0.05) respectively. HCMV also significantly inhibited the growth of HL-60 cells in three different concentrations of viral infection groups (101pfu/ml, 102pfu/ml, 103pfu/ml). After incubation for 7 days, viability cells in control group and each infection groups (n=20) were 96%, 83%, 73%, and 64%, showing that HCMV infection decreased the viability of HL-60 cells in a dose-dependent manner. The apoptotic effect was also investigated by Annexin V assay using flow cytometry. The percentage of Annexin V -positive cells were 19.60 ± 1.63 (in group of 101pfu/ml) (P<0.05), 28.70 ± 2.61 (102pfu/ml) (P<0.05), and 36.3 ± 2.57 (103pfu/ml) (P<0.01), compared with control group 3.96 ± 1.75 (n=8). The apoptotic cells were further confirmed by morphologic observation and DNA ladder formation. Furthermore, HCMV DNA was positive in HL-60 cells and cells of CFU-GM measured by PCR and IS-PCR analysis respectively. These were negative in blank and mock control groups. Our data demonstrated that: (1) HCMV AD169 strain inhibited the growth of HL-60 and CFU-GM formation in a dose-dependent manner; (2) HCMV transcription occurred in HL-60 and CFU-GM cells; and (3) This virus induced apoptosis in HL-60 cells. HCMV may have an inhibiting effect on granulopoiesis via direct infection and inducing apoptosis on myeloid progenitors.

Differences in DNA Packaging Genes and Sensitivity to Benzimidazole Ribonucleosides between Human Cytomegalovirus Strains AD169 and Towne

The AD169 strain of human cytomegalovirus was approximately twofold more sensitive to poly-halogenated benzimidazole ribonucleosides than Towne strain. Sequence differences between the two strains have been identified in genes UL51, UL52, UL56, UL77, UL89 and UL104. Because these genes are involved in cleavage and packaging of viral DNA and the benzimidazole ribonucleosides inhibit this process, these sequence differences may be involved in the difference in drug sensitivity.

Human Cytomegalovirus UL36 Protein Is Dispensable for Viral Replication in Cultured Cells

ABSTRACT Consistent with earlier analyses of human cytomegalovirus UL36 mRNA, we find that the UL36 protein is present throughout infection. In fact, it is delivered to the infected cell as a constituent of the virion. Curiously, much less UL36 protein accumulated in cells infected with the AD169 strain of human cytomegalovirus than in cells infected with the Towne or Toledo strain, and localization of the protein in cells infected with AD169 is strikingly different from that in cell infected with the Towne or Toledo strain. The variation in steady-state level of the proteins results from different stabilities of the proteins. The UL36 proteins from the three viral strains differ by several amino acid substitutions. However, this variability is not responsible for the different half-lives because the AD169 and Towne proteins, which exhibit very different half-lives within infected cells, exhibit the same half-life when introduced into uninfected cells by transfection with expression plasmids. We demonstrate that the UL36 protein is nonessential for growth in cultured cells, and we propose that the ability of the virus to replicate in the absence of UL36 function likely explains the striking strain-specific variation in the half-life and intracellular localization of the protein.

Flow Cytometric Determination of Ganciclovir Susceptibilities of Human Cytomegalovirus Clinical Isolates

A flow cytometric assay has been developed for the measurement of susceptibilities to ganciclovir of laboratory strains and clinical isolates of human cytomegalovirus (HCMV). The assay uses fluorochrome-labeled monoclonal antibodies to HCMV immediate-early and late antigens to identify HCMV-infected cells and flow cytometry to detect and quantitate the number of antigen-positive cells. By this assay, the 50 and 90% inhibitory concentrations (IC50 and IC90, respectively) of ganciclovir for the AD169 strain of HCMV were 1.7 and 9.2 μM, respectively, and the IC50 for the ganciclovir-resistant D6/3/1 derivative of the AD169 strain was greater than 12 μM. The ganciclovir susceptibilities of 17 HCMV clinical isolates were also determined by flow cytometric analysis of the effect of ganciclovir on late-antigen synthesis in HCMV-infected cells. The average IC50 of ganciclovir for drug-sensitive HCMV clinical isolates was 3.79 μM (±2.60). The plaque-reduction assay for these clinical isolates yielded an average IC50of 2.80 μM (±1.46). Comparison of the results of the flow cytometry assays with those obtained from the plaque-reduction assays demonstrated acceptable bias and precision. Flow cytometric and plaque-reduction analysis of cells infected with ganciclovir-resistant clinical isolates failed to show a reduction in the percentage of late-antigen-positive cells or PFU, even at 96 μM ganciclovir. The flow cytometric assay for determining ganciclovir susceptibility of HCMV is quantitative, and objective, and potentially automatable, and its results are reproducible among laboratories.

Computer matching of oligonucleotide patterns on electrophoretic gels: an application to the epidemiology of cytomegalovirus

SummaryA computer program was written to analyse oligonucleotide patterns displayed by gel electrophoresis following restriction endonuclease digestion of human cytomegaloviral DNA, and was applied to an epidemiological study of the transmission of infection in a hospital special care baby unit, with regard to infant-to-infant and mother-to-infant transmission.The program calculates the molecular weight of oligonucleotides from their mobilities, using a cubic spline curve based on the mobilities of oligonucleotides from the AD169 strain. A matching algorithm then calculates the number of unmatched fragments for each pair of viral isolates. This was used as a similarity measure which successfully distinguished mother and infant isolate pairs from epidemiologically unrelated pairs.The program is not intended to provide fully automatic matching, but could be recommended as a screening device to pick out pairs of strains which are sufficiently similar to suggest a common source of infection, and which may warrant closer comparison. Other applications are discussed, and the possible use of densitometers to automate data entry is considered.